Maintenance Commands listen(1M)



NAME
listen - network listener daemon

SYNOPSIS
/usr/lib/saf/listen [ -m devstem ] net_spec

DESCRIPTION
The listen process ``listens'' to a network for service
requests, accepts requests when they arrive, and invokes
servers in response to those service requests. The network
listener process may be used with any connection-oriented
network (more precisely, with any connection-oriented tran-
sport provider) that conforms to the Transport Layer Inter-
face (TLI) Specification.

The listener internally generates a pathname for the minor
device for each connection; it is this pathname that is used
in the utmpx entry for a service, if one is created. By
default, this pathname is the concatenation of the prefix
/dev/netspec with the decimal representation of the minor
device number. In either case, the representation of the
minor device number will be at least two digits (for exam-
ple, 05 or 27), or longer when it is necessary to accommo-
date minor device numbers larger than 99.

SERVER INVOCATION
When a connection indication is received, the listener
creates a new transport endpoint and accepts the connection
on that endpoint. Before giving the file descriptor for this
new connection to the server, any designated STREAMS modules
are pushed and the configuration script is executed, (if one
exists). This file descriptor is appropriate for use with
either TLI (see tync(3NSL) ) or the sockets interface
library.

By default, a new instance of the server is invoked for each
connection. When the server is invoked, file descriptor 0
refers to the transport endpoint, and is open for reading
and writing. File descriptors 1 and 2 are copies of file
descriptor 0; no other file descriptors are open. The ser-
vice is invoked with the user and group IDs of the user name
under which the service was registered with the listener,
and with the current directory set to the HOME directory of
that user.

Alternatively, a service may be registered so that the
listener will pass connections to a standing server process
through a FIFO or a named STREAM, instead of invoking the
server anew for each connection. In this case, the connec-
tion is passed in the form of a file descriptor that refers
to the new transport endpoint. Before the file descriptor is
sent to the server, the listener interprets any



SunOS 5.8 Last change: 3 Apr 1997 1






Maintenance Commands listen(1M)



configuration script registered for that service using
doconfig(3NSL), although doconfig is invoked with both the
NORUN and NOASSIGN flags. The server receives the file
descriptor for the connection in a strrecvfd structure using
an IECVFD ioctl(2).

For more details about the listener and its administration,
see nlsadmin(1M).

OPTIONS
-mdevstem
The listener will use devstem as the prefix for the
pathname.

FILES
/etc/saf/pmtag/*

ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:


| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|||
| Availability | SUNWcsu |
|||


SEE ALSO
nlsadmin(1M), pmadm(1M), sac(1M), sacadm(1M), ioctl(2),
doconfig(3NSL), nlsgetcall(3NSL), nlsprovider(3NSL),
tync(3NSL), attributes(5), streamio(7I)

System Administration Guide, Volume 1

NOTES
When passing a connection to a standing server, the user and
group IDs contained in the strrecvfd structure will be those
for the listener (that is, they will both be 0); the user
name under which the service was registered with the
listener is not reflected in these IDs.

When operating multiple instances of the listener on a sin-
gle transport provider, there is a potential race condition
in the binding of addresses during initialization of the
listeners, if any of their services have dynamically
assigned addresses. This condition would appear as an ina-
bility of the listener to bind a static-address service to
its otherwise valid address, and would result from a
dynamic-address service having been bound to that address by
a different instance of the listener.




SunOS 5.8 Last change: 3 Apr 1997 2